In IP communications, a set of end points have either fixed or dynamic addresses. Dynamic addressing (either public or private) can be achieved using dynamic host configuration protocol (DHCP); authentication, authorization accounting protocol (AAA); or other protocols known by those skilled in the art. However, even with dynamic addressing, typically only clients have a dynamic address, while server addresses are typically fixed.
Mobile IP is a protocol which allows transparent routing of IP datagrams (or packets) to laptop computers or other mobile clients (referred to as “Mobile Nodes” herein), enabling the mobile nodes (MN) to roam between various sub-networks at various locations—while maintaining internet and/or WAN connectivity. Without Mobile IP or a similar protocol, a Mobile Node would be unable to stay connected while roaming through various sub-networks because the IP address required for any node to communicate over the internet is location specific. Each IP address has a field that specifies the particular sub-network on which the node resides. While away from home, a MN is associated with a home agent address HA′, which is traditionally static, and gives information about the MN's current locations. Mobile IP specifies how a MN registers with its home agent (HA) and how the HA routes packets to the MN through a tunnel.
Unfortunately, the fact that the static HA′ is known to the MN may lead the home agent open to attacks.